1. Field of The Invention
Described are novel polypeptides, DNA sequences and plasmids relating to novel modified human gamma-like interferons useful in pharmaceutical compositions.
2. Background of The Invention
Interferons (IFNs) are a family of proteins synthesised in mammalian cells in response to stimulation by viruses, mitogens and a variety of other substances. Initial studies on interferon concentrated on its ability to induce an antiviral state in target cells. More recently, interferon has been shown to inhibit cell proliferation and to modulate the immune response (1).
The interferons have potential used in the treatment of viral infections and malignant disease. The natural amino acid sequence and DNA sequence of Human Immune (gamma) Interferon was diclosed in UK patent application No. GB 2 107 718 A and European patent application No. 0088540A2.
Human interferons have been classified into 3 groups according to their antigenic, biological and chemical properties: IFN-alpha (leucocyte), IFN-beta (fibroblast) and IFN-gamma (immune). The virus induced, acid stable interferons (IFN-alpha and IFN-beta) have been studied in the greatest detail. The use of recombinant DNA technology has allowed the deduction of amino acid sequences of IFN-beta and several species of IFN-alpha. IFN-gamma is acid labile and does not cross react with antisera to IFN-alpha and IFN-beta. IFN-gamma possesses a wide range of biological activities (2,3,4). IFN-gamma potentiates the antiviral activity of IFN-alpha and IFN-beta but differs from the acid stable interferons in its virus and target cell specificity (2). However, in vitro studies with impure IFN-gamma indicate that one important activity of IFN-gamma is to regulate the immune response (3). Since the anti-proliferative effect of IFN-gamma on transformed cells is up to 100.times. that of either IFN-alpha or IFN-beta (4), IFN-gamma may be useful in the treatment of malignant disease. Mouse IFN-gamma shows significant anti-tumour activity against mouse sarcoma (5). The cDNA coding for human IFN-gamma has been cloned in E. coli (6,7). The amino acid sequence of IFN-gamma has been deduced and it has been shown that the mature polypeptide is 146 amino acids long. IFN-gamma has been expressed in E. coli and in a eukaryotic system (6). The levels of expression are much lower than those observed with IFN-alpha and IFN-beta in similar expression systems.
Modified interferon gammas have been described that contain a deleted cys-1, tyr-2, cys-3 (PCT application No. 83/04053). However, they do not disclose the modified interferon gammas of the present invention.
The synthetic human gamma interferon gene in plasmid pCC 203 was previously disclosed and deposited in the American type culture collection as ATCC 39494. The addition of polyarginine to polypeptides to facilitate purification was previously described (8).